Method of open-pit mining

ABSTRACT

A method of open-pit mining according to which a transport ramp system is provided in a tunnel system outside the open pit and the body of materials which is mined for establishing communication between the surface and the different mining levels.

United States Patent Henriksson et a1.

METHOD OF OPEN-PIT MINING Inventors: Sune Torsten Henrikson, Kvartsvagen6; Ragnar Ludvig Muotka, Kyrkogatan 46, both of 981 00 Kimna, SwedenFiled: Oct. 29, 1970 App1.No.: 84,963

Foreign Application Priority Data Oct. 31, 1969 Sweden ..l4945/69 US. Cl..299/l8, 299/19 Int. Cl ..E21c 41/00 Field of Search ..299/18, 19;37/195; 61/5,

[4 Sept. 19, 1972 t [56.] References Cited UNITED STATES PATENTS3,167,354 1/1965 Macaul et a1. ..299/l8 X 3,582,138 6/1971 Loofbourow eta1. ..299/l8 Primary Examiner-Emest Purser Attorney-Jones & Lockwood[57] ABSTRACT A method of open-pit mining according to which a transportramp system is provided in a tunnel system outside the open pit and thebody of materials which is mined for establishing communication betweenthe surface and the different mining levels.

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METHOD OF OPEN-PIT MINING The present invention relates to mining and,in particular, to a method of open-pit mining.

In an open-pit mine which is used when the deposit of ore or minerals tobe mined starts from or lies adjacent to the surface of the ground it isknown to establish communications between the working site or the mininglevel in question and the surface by means of a transport track or rampwhich extends from the surface downwardly along the walls of theopen-pit mine which are formed accordingly as the mining progresses. Foreach new mining level a new transport ramp must be established, and oreor other materials which are mined must be carried away. Also thematerial surrounding the ore or mineral body which is mined must beremoved. in that connection such a quantity of the surrounding materialmust be removed that the slope stability required in each particularcase is obtained in the walls of the open-pit mine and that thenecessary space is obtained for the inclined track or ramp extendingalong said walls. As the transport ramp must have a width of to 13meters including the requisite protective wall at the outer side of theramp, the building of the transport ramp entails a substantial increaseof the quantity of materials which have to be removed, in addition tothe quantity of materials required in order to obtain the necessaryslope stability. It will therefore be realized that the quantity ofmaterials which increases in proportion to the distance of the transportramp from the surface of the ground must be carried away when a lengthunit of the ramp is built since for obtaining each surface unit of thetransport ramp it is necessary to remove a volume .of materialscorresponding to the surface unit in question multiplied by its distanceto the surface of the ground. In an openpit mine of a great depth thebuilding of the inclined track or ramp will consequently entailconsiderable building costs.

Not only the building costs but also the maintenance costs are howeververy high when using transport ramps of the known kind described above.Thus, for safety reasons it is necessary to clear the rock wall abovethe transport ramp, which cannot be done once only when the ramp isbuilt but has to be performed at even time intervals due to the factthat the rock wall will weather under the action of the climate. Sincethe surfaces to be cleared are very large and the work is risky and timeconsuming especially when there is ice and snow the costs in thisconnection are substantial.

When the road is very slippery and when great amounts of snow and rainhave fallen it may become necessary to interrupt traffic on thetransport ramp completely which, as will be realized, makes it necessaryto stop the mining after a short time. Such a total stop may entaillosses amounting to tens of thousands of dollars per hour. In tropicalcountries the stop may have to be total for several weeks during therains, when it may also happen that the transport ramp is completelydestroyed.

There is an additional problem in connection with snowfall, as the snowmust be conveyed down to the bottom of the pit, where it has to beloaded onto trucks and then carried up to the surface. It will-berealized that this complicated method of removing snow from thetransport ramps and roads is very expensive.

The object of the invention is consequently to provide a method ofopen-pit mining in which the establishing of communications betweenvarious mining levels and the surface of the ground is more inexpensiveboth with regard to the building costs and with regard to themaintenance costs thanin connection with the known methods of mining.

This object is attained according to the invention by building thetransport tracks or ramps in tunnels in the mountain outside the body ofmaterials which is mined.

The building costs for an inclined track or a ramp built in a tunnel areconsiderably lower than for a ramp built in open air in a conventionalmanner. It is true that the costs per unit of volume ofremoved'materials will be slightly higher when the ramp or track isbuilt in a tunnel but these increased costs are more than compensatedfor by the fact that a very much smaller volume of materials has to beremoved per built surface unit of the inclined track or ramp when thelatter is built in a tunnel. Evidently, there is required for eachsurface unit of the ramp a constant volume of removed materialsindependently of the distance of the ramp from the surface, and thecosts saved when applying the method according to the invention willconsequently become proportionally higher accordingly as the depth ofthe open-pit-mine increases. Thus, for instance, for an open pit havinga depth of 500 meters the costs for building an inclined track in themanner according to the invention have been assessed to amount to only2.8 per cent of the costs for building a conventional transport ramp inthe open air.

As also the maintenance costs of a transport track or ramp built in atunnel'will for obvious reasons beconsiderably lower than with respectto a conventional 'rampit will be realized that the savings which can bemade when applying the mining method according to the invention areconsiderable. No cleaning of large surfaces is required and besides,therisks of slipping when there is ice and snow as well as theinterruptions of the operation due to the action of the climate arecompletely eliminated.

The position of the transport ramp must be determined from case to casein view of the shape of the body of materials which is mined, the typeof materials in the body and the materials surrounding it, etc. Thus,the transport ramp may extend around the body of materials or may belocated serpentine-like on one side thereof.

Connections are built between the ramp and the working sites on thedifferent levels, and these connections are planned according to thesame principles as in a ramp system built in open air.

The invention will be described in greater detail in the following withreference to the accompanying drawings, where FIGS. la and 1b arediagrammatic views of a manner of arranging a transport ramp accordingto the invention,

FIGS. 2a and 2b are also diagrammatic views of another manner ofarranging a transport ramp according to the invention,

FIG. 3 shows a way of arranging the connection between the inclinedtrack and the surface of the ground, and

FIG. 4 shows another manner of arranging the connection of the inclinedtrack with the surface of the ground.

FIGS. 'la and lb are diagrammatic views of an ore body 1 which is to bemined according to the open-pit mining method. In order to obtain thenecessary slope stability the surrounding rock 2 must be removed alongthe lines 3 and 4 accordingly as the mining progresses. Communicationswith the mining levels which will be located at longer and longerdistances from the surface of the ground is obtained by means of atransport ramp or an inclined track 5 built in a tunnel which extendsserpentine-like at the righthand side of the ore body in the figure,i.e., on the so called foot wall side of the ore body, and by means ofhorizontal tunnels 6 extending from the transport ramp to the workingsites. When building the tunnels it is possible, if necessary, toreinforce the tunnel walls by means of rock bolts and the like,whereupon the communication system may be regarded as almostmaintenance-free. The only kind of maintenance which is normallyrequired is consequently the maintenance of the transport ramp, which isworn by the vehicle traffic.

FIGS. 2a and 2b show another ore body 7. In this case it has beenconsidered suitable to let the transport ramp 8 extend in a tunnelrunning helically around the ore body. In this case, too, communicationis established between the ramp and the working sites by means ofhorizontal tunnels 9. The rock surrounding the ore body is removed inthe ordinary manner along the lines 10 and 11 in order to achieve therequisite slope stability.

FIG. 3 shows the embodiment of a connection between a ramp 12 built inthe tunnel and the surface of the ground. As appears from the figure,the tunnel and consequently the ramp has a section 13 at the orificewhich is inclined outwardly downwardly with an angle of inclination inrelation to the horizontal plane which preferably amounts to 1 to 3. Thepurpose of giving the top section of the ramp an inclination which isopposite to the rest of the transport ramp in relation to the horizontalplane is of course to prevent rain and snow from entering thecommunication system and cause difficulties of various kinds there.Since the tunnel in the case shown opens into an inclined portion of thesurface of the ground a roof or cover above the top section of thetransport ramp is automatically obtained.

FIG. 4 shows how the tunnel opens at a plane part of the surface of theground and in this case it is necessary to build a specialsuperstructure 14 in order to cover the opening of the tunnel.

It will be realized that the invention can be modified within the scopeof the following claims, and particularly with regard to the extensionof the inclined track and consequently of the tunnel system in relationto the body of materials where the mining takes place the application ofthe invention must be determined from case to case.

We claim:

1. A method for transporting ore upwardly from a deep open-pit mine tothe ground surface, which method comprises the steps of:

a. forming a downwardly inclined tunnel system from the ground surfaceand extending the tunnel s st d nwardl throu h the ater'als 'n oirts iia ofihe open pit min parts 0 sai out yin tunnel system being formed incommunication with the open-pit mine; v

b. providing an inclined transport ramp system throughout said tunnelsystem;

c. transporting ore on said ramp system from the open-pit mine andthrough the tunnel formed in the materials lying outside of the open-pitmine; and

d. recovering the ore at the ground surface.

2. The open-pit mining method of claim 1 which the outlying tunnelsystem is formed helically around the open-pit mine.

3. The open-pit mining method of claim 1 in which the tunnel system isformed serpentine-like at one side of the open-pit mine.

4. The open-pit mining method of claim 1 in which substantiallyhorizontal tunnels are provided in communication between the downwardlyinclined tunnel system and the open-pit mine.

5. The open-pit mining method of claim 1 in which the transport rampsystem is provided with an outwardly-downwardly sloping ramp section atthe junction of the. ramp system and the ground surface.

6. The open-pit mining method of claim 1 in which the downwardlyinclined tunnel system is provided with a superstructure at the junctionof the tunnel system and the ground surface.

I ii

1. A method for transporting ore upwardly from a deep open-pit mine tothe ground surface, which method comprises the steps of: a. forming adownwardly inclined tunnel system from the ground surface and extendingthe tunnel system downwardly through the materials lying outside of theopen-pit mine, parts of said outlying tunnel system being formed incommunication with the open-pit mine; b. providing an inclined transportramp system throughout said tunnel system; c. transporting ore on saidramp system from the open-pit mine and through the tunnel formed in thematerials lying outside of the open-pit mine; and d. recovering the oreat the ground surface.
 2. The open-pit mining method of claim 1 whichthe outlying tunnel system is formed helically around the open-pit mine.3. The open-pit mining method of claim 1 in which the tunnel system isformed serpentine-like at one side of the open-pit mine.
 4. The open-pitmining method of claim 1 in which substantially horizontal tunnels areprovided in communication between the downwardly inclined tunnel systemand the open-pit mine.
 5. The open-pit mining method of claim 1 in whichthe transport ramp system is provided with an outwardly-downwardlysloping ramp section at the junction of the ramp system and the groundsurface.
 6. The open-pit mining method of claim 1 in which thedownwardly inclined tunnel system is provided with a superstructure atthe junction of the tunnel system and the ground surface.